The construction industry is under constant pressure to provide quality products at low cost. Door frames are no exception.
During construction of a home or the like, an opening is left in the wall in which the door or window is installed. In some cases, a custom door frame is built in the door opening. After the door frame is built, the door is hung within the door frame. While this provides builders complete control, such a construction technique can be time consuming and costly. Measurements and construction must be very precise to accurately place the door frame into the opening and account for small variations in the door.
Another method of hanging frames is with the use of pre-hung doors or windows. In this case, a completed frame and door is provided to the builder. An example of an adjustable door frame assembly is found in U.S. Pat. No. 3,812,621. Thus, the frame and door are pre-matched for tighter fitting door or windows.
One known method of providing pre-built frames at a low cost is with the use of scrap lumber. Scrap lumber is produced when a defect, such as a knot hole or imperfect edge, is removed from a larger or parent piece of lumber. This allows the parent lumber to be sold as a higher quality piece than it otherwise would. The resulting scrap piece containing the defect is typically much smaller than its parent piece. The scrap lumber is then processed or recycled by removing the defect to produce a relatively small, but still good quality piece of wood fiber. These small pieces are then finger jointed at their ends and joined end to end to produce a single long piece, which is used to produce the door frame.
Norlander in U.S. Pat. No.5,074,092 describes a technique for overcoming certain deficiencies with inexpensive lumber having a variety of knots and other defects. Quality veneers are assembled with cores of short end-to-end staves of solid lumber to produce a laminated wood door product having stability and good appearance.
While these techniques have produced low cost door and window frames, the use of wood in them causes the frames to be susceptible to moisture and insects. In the past, once water or termite damage has caused a portion of the frame to decay, that portion of the frame was replaced. Repair was performed while the frame was in place. A craftsman would cut out the decayed portion and replace it with another wood or plastic section. Thus, while costs were initially low, the end result was often expensive.